Relationship between Serum Cholesterol and Aortic Lipid Content and Effect of EPL® on Lipid Accumulation of Rabbit Aortas on High Cholesterol Diet

It is well known that the increase of serum cholesterol causes the accumulation of cholesterol ester (CE) in aortas and that lowering serum cholesterol level prevents atherosclerosis. But the precise relationship between serum cholesterol level and CE accumulation in the aortas is not clear. The purpose of this study is to clarify the relationship between serum cholesterol level and CE content of rabbit aortas, and to clarify whether CE content of aortas is lowered by some mechanisms other than lowering serum cholesterol level. When serum cholesterol level is increased linearly with feeding period, it is suggested that cholesterol exposure to aortas is expressed as (serum cholesterol)×(feeding period)×1/2 and so we named (serum cholesterol level)×(feeding period)×1/2 as accumulated cholesterol index. To clarify the relationship between accumulated cholesterol index and CE content of aortas and effects of EPL on lipid accumulation in the aortas, rabbits were fed on 0.5% cholesterol diet for 8-20 weeks with or without EPL. The relationship between accumulated cholesterol index and CE content of aortas on high cholesterol diet was not linear, but CE content was increased steeply when accumulated cholesterol index ranged from 500 to 3, 000 and CE content was increased slowly when the index was below 500 or over 3, 000. If the effect of EPL is only to the decreased serum cholesterol level, CE content of aortas with EPL will be estimated by the relationship between accumulated cholesterol index and CE content. But the relationship between accumulated cholesterol index and CE content of aortas with EPL was deviated and CE content with EPL was lower than CE content estimated by the relationship between accumulated cholesterol index and CE content. These results suggested that CE content of aortas is decreased by EPL not only by the mechanism of lowering serum cholesterol level but also by some mechanisms other than lowering serum cholesterol level.